The use of a water separator in a diesel engine is a well-known expedient to rid the fuel of water that might cause malfunction of the engine. Typical water separators consist of some type of water collection reservoir at the bottom of a fuel filter assembly, and various techniques have been employed to monitor the amount of water accumulated therein.
One known technique for monitoring the amount of water collected in a fuel filter assembly includes locating a water-in-fuel sensor within the water collection reservoir. When the water level reaches a predetermined level in the reservoir, the sensor is activated and a warning indicator is correspondingly energized. Typically, the warning indicator comprises a signal lamp mounted in the cab area of the vehicle so that the driver is apprised of the need to drain the fuel filter assembly.
Diesel engines, as with other internal combustion engines, further typically include an engine cooling system containing an engine coolant fluid that circulates about the engine to maintain the engine operating temperature within a desired temperature range. It is commonplace in such diesel engines to include an engine coolant level sensor therein so that the vehicle control computer may monitor the coolant level. Due to the importance of the engine cooling system, typical engine coolant level sensors provide redundant sensor signals to the vehicle control computer which then acts on these signals to store diagnostic information related to the engine cooling system as well as warn the operator of low engine coolant level conditions.
One problem with the foregoing known sensor arrangements is that the water-in-fuel sensor may or may not be monitored by the vehicle control computer. If it is, then the vehicle control computer must provide an additional input signal path to receive the water-in-fuel sensor signal. Often times, an extra input signal path to the vehicle control computer is simply not available and the water-in-fuel sensor signal is directed to a lamp driving circuit separate from the vehicle control computer. In such cases, the vehicle control computer cannot monitor the water-in-fuel sensor status and likewise cannot store diagnostic information related thereto.
What is therefore needed is a system for processing output signals associated with multiple vehicle condition sensors, such as a water-in-fuel sensor and an engine coolant level sensor, which does not increase the number of required input signal paths to the vehicle control computer, yet provides for complete status and diagnostic monitoring of each of the sensors.